Don't know how fast Citrix CPU was in games (But I have one in my collection of old CPUs. Looks funny, you know. :) )
But on my lightning-fast 486dx2 I've played in F-19, F-117, LHX, Strike Commande and Gunship sims, Tie-Fighter runs fast and smoothly.
I'ts funny, cause now my old PocketPC is triply faster than that antiques old-man. :)
BTW - as far as I remember - SU-27 are flying with 486 CPU, and Space Shuttles with Pentium 1.